old55pete Posted May 4, 2020 Author Share Posted May 4, 2020 Hi pete , if none of that works , i had some really high idle issues and it was a plug down beside the trans , i suppose it tells the computor that the trans is in gear , i ended up disconnecting it and putting a jumper in . That was one of my high idle experiences! In my truck, Crazy computors , also watch that pcv valve it supplys a lot of air and is a percentage of the idle air , a new one that i bought flowed so much air the valve inside sounded like a small motor . , but that would be more constant high idle , anyway I used a plastic body pcv that seemed to flow less this meant i could increase my base idle to give the iac less to do , and my truck wouldn't surge and die .stuff to think about . Cheers Thank you gentlemen, I will give it all a try and let you know what worked. It might be a spell as I am in the middle of selling my business. Thank you all. Link to comment Share on other sites More sharing options...
Gearhead Posted May 14, 2020 Share Posted May 14, 2020 Im reaching back into my past...had an 86 5.0 efi Speed density also...seems like I had a similar issue once. Isnt the throttle air bypass valve you speak of called an IAC solenoid? Maybe that is malfunctioning. Im sure you can test the voltage coming to it. I'll see if I can find something. IAC's were a big problem. Never heard of one making a mechanical popping sound. Has anyone figured out where that noise is coming from? Typically the IAC would sludge up, and so would the throttle plate, due to the crank vent hose location causing higher idle. The sludge is best cleaned by removing the IAC and cleaning it out with carb clean. I believe that prior to 89 the throttle plate could be cleaned with carb clean, after that there was a coating on the throttle plate the carb clean would eat off causing idle issues. You cleaned those by removing them and scrubbing with soap and water. The noise could be the big clue see if you can find where it's coming from. Another thing causing elevated idle would be a vacuum leak, but those usually are high and stay that way. Link to comment Share on other sites More sharing options...
old55pete Posted June 28, 2020 Author Share Posted June 28, 2020 IAC's were a big problem. Never heard of one making a mechanical popping sound. Has anyone figured out where that noise is coming from? Typically the IAC would sludge up, and so would the throttle plate, due to the crank vent hose location causing higher idle. The sludge is best cleaned by removing the IAC and cleaning it out with carb clean. I believe that prior to 89 the throttle plate could be cleaned with carb clean, after that there was a coating on the throttle plate the carb clean would eat off causing idle issues. You cleaned those by removing them and scrubbing with soap and water. The noise could be the big clue see if you can find where it's coming from. Another thing causing elevated idle would be a vacuum leak, but those usually are high and stay that way. Sorry I haven't done anything with this in a while. It has been a wild couple of months to say the least. As a couple of you stated, I first checked the grounds and found a couple that needed attention. One was the brand new battery cable on the neg post. Im not sure whats up with that, but after cleaning the inside with a terminal brush, I tested with a multimeter and found it to have no resestance. I also found the ground between the fire wall and the back corner of the intake was broken and repaired that too None of these fixed the problem. I again smoke tested it and dident find a single leak so I moved in to the IAC or idle air control valve. I pulled it off and for the most part it was clean as a whistle, both inside the valve and the ports into the throttle body. I sprayed some PB Blaster into the valve and it worked fine for a couple of days and then went back to the same old story. I found a NOS IAC on ebay thanks to Garys extencive parts lists and installed it today, along with a new throttle cable. Another story for another time as I need to sort that one out Link to comment Share on other sites More sharing options...
old55pete Posted June 28, 2020 Author Share Posted June 28, 2020 IAC's were a big problem. Never heard of one making a mechanical popping sound. Has anyone figured out where that noise is coming from? Typically the IAC would sludge up, and so would the throttle plate, due to the crank vent hose location causing higher idle. The sludge is best cleaned by removing the IAC and cleaning it out with carb clean. I believe that prior to 89 the throttle plate could be cleaned with carb clean, after that there was a coating on the throttle plate the carb clean would eat off causing idle issues. You cleaned those by removing them and scrubbing with soap and water. The noise could be the big clue see if you can find where it's coming from. Another thing causing elevated idle would be a vacuum leak, but those usually are high and stay that way. Sorry I forgot, the popping sound when you push the foot feed, I took it to an AC shop to have it sucked down and recharged so it would work right, it would blow cool but not cold. While they had it they took the cover off of the throttle cable and tried to adjust the idle down by the screw by the cables. The screw wasent even touching the tang and was letting the butterflys jamb closed. With the engine off and the key on I hooked a multimeter to the TPS and adjusted it until I got one volt. That is also now solved. PS They gave me an estimet for $3000.00 to repair the AC, they wanted to rebuild the whole system. Sad part was it was working. What a ripoff joint that turned out to be. Link to comment Share on other sites More sharing options...
Gary Lewis Posted June 29, 2020 Share Posted June 29, 2020 Sorry I forgot, the popping sound when you push the foot feed, I took it to an AC shop to have it sucked down and recharged so it would work right, it would blow cool but not cold. While they had it they took the cover off of the throttle cable and tried to adjust the idle down by the screw by the cables. The screw wasent even touching the tang and was letting the butterflys jamb closed. With the engine off and the key on I hooked a multimeter to the TPS and adjusted it until I got one volt. That is also now solved. PS They gave me an estimet for $3000.00 to repair the AC, they wanted to rebuild the whole system. Sad part was it was working. What a ripoff joint that turned out to be. Wow! $3000!!!! You can buy a running truck for that! But glad you got the problem solved with the idle. Link to comment Share on other sites More sharing options...
old55pete Posted July 5, 2020 Author Share Posted July 5, 2020 Wow! $3000!!!! You can buy a running truck for that! But glad you got the problem solved with the idle. Yes sir, the AC shop dident much like it when I told them that I already owned the car and all I wanted was the system evacuated and re charged, a simple enough request I thought. Link to comment Share on other sites More sharing options...
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